1. Field of the Invention
The present invention relates to an electronic apparatus having a keyboard, and more particularly to an improvement in such apparatus having a foldable structure.
2. Description of the Prior Art
Conventional electronic apparatus such as electronic calculators are generally provided with plural key switches arranged on a plane, as input means, which increase in number in case of varied input information must be input such as in functional calculators or programmable calculators. Therefore, the calculators require a large keyboard that is often inconvenient for carrying.
Also the electronic calculators with a character display function have recently become very popular with the public and acquired the function of electronic memorandum or diary, with electronic display of various information.
The display devices of the segment type, being incapable of alphanumeric display, are generally inadequate for providing such a memorandum function which requires an increased amount of information display. For this reason, in such electronic apparatus, the display devices have been improved and are of the dot matrix type with a small dot pitch to enable alphanumeric display and to indicate the usual memorandum message by means of the increased number of dots.
In such electronic apparatus, for example an electronic calculator with memorandum function, portability is however an essential factor, so that the number of characters displayable on the dot-matrix display device is usually limited as the keyboard requires a considerable amount of space.
On the other hand the memorandum function requires a considerable number of characters for each message. For this reason there has been proposed a moving display, in which the message to be displayed is supplied, beginning with a leading character, to one end of the display device on a character by character basis. After characters comprising the message fill the available display spaces of the device, the displayed message is extinguished on a similar character by character basis from the one end of the display device whle characters comprising the message are added to the one end, thereby enabling the display of many characters. Display of the message in plural divided portions has also been proposed.
However, such display methods do not allow confirmation of entire message at one time, but require a certain time for message reading and thus present a danger of erroneous reading. There has therefore ben proposed a display method employing multi-row display device to display the entire message at the same time. Such a display device however requires a considerable area, limiting the space available for the keyboard for the entry or readout of memorandum messages or for performing calculator operation.
On the other hand the message entry also requires an increased number of keys such as alphabet keys. As a result such electronic apparatus with a memorandum function require large spaces both for the display and for the keyboard, and become excessively large for carrying and lose the most important advantage of apparatus of this sort.
In order to circumvent such drawback there is already proposed, for example as disclosed in the U.S. Pat. No. 4,395,704 of the present applicant, a foldable structure composed of a display unit and a keyboard unit which are foldably connected to be opened for use and closed for carrying.
Such known foldable apparatus is designed to be opened for observing the memorandum message but is provided with another segment-type display device exclusively for frequently used arithmetic calculations and time indication in a position observable even in the folded state of the apparatus. Such structure however requires large manufacturing costs, since it uses two separate display devices.
Also in case of an electronic calculator with many functional operations, there is required a quite large number of keys which inevitably increases the size of the calculator itself, thus leading to increased manufacturing cost and limiting the portability of the apparatus even if such keys can be accommodated in a foldable structure composed of two halves, one of which is provided with plural keys and the of which other is provided with a display device and remaining keys.